The present invention relates in general to the design and construction of self-driven centrifugal separators with disposable component parts. More specifically, a first embodiment of the present invention relates to the design and construction of a self-driven, cone-stack centrifuge wherein the entire cone-stack assembly and rotor shell combination is designed to be disposable, including the structural configuration as well as the selected materials. In a related embodiment, all of the disposable-design features are retained, but the cone-stack subassembly is removed.
The evolution of centrifugal separators, self-driven centrifuges, and cone-stack centrifuge configurations is described in the Background discussion of U.S. Pat. No. 5,637,217 which issued Jun. 10, 1997 to Herman, et al. The invention disclosed in the ""217 Herman patent includes a bypass circuit centrifuge for separating particulate matter out of a circulating liquid which includes a hollow and generally cylindrical centrifuge bowl which is arranged in combination with a base plate so as to define a liquid flow chamber. A hollow centertube axially extends up through the base plate into the hollow interior of the centrifuge bowl. The bypass circuit centrifuge is designed so as to be assembled within a cover assembly. A pair of oppositely disposed tangential flow nozzles in the base plate are used to spin the centrifuge within the cover so as to cause particulate matter to separate out from the liquid. The interior of the centrifuge bowl includes a plurality of truncated cones which are arranged into a stacked array and are closely spaced so as to enhance the separation efficiency. The incoming liquid flow exits the centertube through a pair of fluid (typically oil) inlets and from there is directed into the stacked array of cones. In one embodiment, a top plate in conjunction with ribs on the inside surface of the centrifuge bowl accelerate and direct this flow into the upper portion of the stacked array. In another embodiment of the ""217 invention the stacked array is arranged as part of a disposable subassembly. In each embodiment, as the flow passes through the channels created between adjacent cones, particle separation occurs as the liquid continues to flow downwardly to the tangential flow nozzles.
While this prior patent discloses a disposable subassembly, this subassembly does not include the rotor top shell or what is called the permanent centrifuge bowl 197 in the ""217 patent, nor the rotor bottom shell or what is called the base 198 in the ""217 patent. Accordingly, in order to actually dispose of subassembly 186 (referring to the ""217 patent), the subassembly must be disassembled from within the rotor shell. In contrast, in one embodiment of the present invention, the entire cone-stack subassembly, as well as the alignment spool, hub, and rotor shell, are all combined into a single, disposable unit. In another embodiment of the present invention, the entire cone-stack subassembly, as well as the spool, hub, rotor shell and both bearings are combined into a single disposable unit.
Earlier products based on the ""217 patent utilize a non-disposable metallic rotor assembly and an internal disposable cone-stack capsule. While these products provide high performance and low life-cycle cost to the end user, there are areas for improvement which are addressed by the present invention. These areas for improvement which are addressed by the present invention include:
1. High initial cost of the centrifuge rotor assembly which consists of an aluminum die-cast rotor, machined steel hub, pressed in journal bearings, two machined nozzle jets, the cone-stack subassembly or capsule, deep-drawn steel rotor shell, O-ring seal, and a large machined xe2x80x9cnutxe2x80x9d to hold everything together. This design approach is best suited for large engines with a displacement of something greater than 19 liters where the initial cost of the centrifuge (and engine) is less important that life-cycle cost. Also, the larger rotor size, coupled with low production volume of these engines leads towards the use of metallic components and the corresponding manufacturing processes.
2. Awkward and time-consuming service. The centrifuge rotor must be disassembled to remove the cone-stack capsule which is a rather messy job to perform, despite the encapsulation of the cone-stack subassembly and the accumulated sludge. With a disposable rotor design, the complete rotor is simply lifted off of the shaft, discarded, and replaced with a new centrifuge rotor assembly.
The disposable centrifuge rotor design of the present invention provides the needed improvements to the problem areas listed above by reducing the initial cost of the rotor subassembly by approximately 75% ($6.00 versus $25.00 for comparably sized rotor of prior design) and by allowing quick and mess-free service. While a majority of the invention disclosure, as set forth herein, is directed to the embodiment that uses a cone-stack subassembly for enhanced separation efficiency, a lower-cost embodiment is also disclosed.
The molded plastic and plastic welded design of the rotor shell of the present invention in combination with the cone-stack subassembly provides improved separation performance compared to all-metal designs. The present invention also provides an incinerable product which is important for European markets. In a related embodiment of the present invention, top and bottom bearings are pressed into the top and bottom rotor shell halves, respectively. These bearings can be oil-impregnated sintered brass, machined brass, or molded plastic. The rotor shell of the present invention also provides a design improvement due to a reduced number of parts which results from the integration offered by molding as compared to metal-stamping designs. The present invention is intended primarily for lube system applications in diesel engines with displacement less than 19 liters. It is also believed that the present invention will have applications in hydraulic systems, in industrial applications such as machining fluid clean up, and in any pressurized liquid system where a high capacity and high efficiency bypass separator is desired.
A disposable, self-driven centrifuge rotor assembly for separating an undesired constituent out of a circulating fluid according to one embodiment of the present invention comprises a first rotor shell portion, a second rotor shell portion joined to the first rotor shell portion so as to define a hollow interior, a support hub positioned within the hollow interior adjacent the second rotor shell portion, an upper alignment spool positioned within the hollow interior adjacent the first rotor shell portion, and a cone-stack subassembly including a plurality of individual separation cones arranged into an aligned stack with flow spacing between adjacent separation cones, the cone-stack subassembly being positioned within the hollow interior between the support hub and the upper alignment spool.
One object of the present invention is to provide an improved self-driven, centrifuge rotor assembly.
Related objects and advantages of the present invention will be apparent from the following description.